Slacktave MKII question

[solderman]

Hi
I have just finished bread boarding the Slaktave MK II and as usual with me and bread boarding it did not fire up at ones. It's always something.. started to probe as usual but did not get any tone from the first OUT on opamp stage one? Did a lot of testing and finally found that the schematics I have used (MK II ver.) has all inverting/non inverting op-amp stages "inverted"  I Changed the fist stage and this stage works now. So I'm gonna rebuild the rest tomorrow.




Q- Is this just a schematics "typo" or is there something I'm missing here?? I am using two TL072


BTW this thing has is a "killer sound" so I am really keen to get it to work. By the samples I have heard. Especially that one that starts with a Wha and adds a Phase90. That smells Kraftwerk. Bet you cloud play "Autobahn" with this one   

http://forum.musikding.de/cpg/thumbnails.php?album=300

Thank's Slacker for designing it and Helge for those recordings I just love them.

[frequencycentral]

BTW this thing has is a "killer sound" so I am really keen to get it to work. By the samples I have heard. Especially that one that starts with a Wha and adds a Phase90. That smells Kraftwerk. Bet you cloud play "Autobahn" with this one   

Damn, I love Autobahn, gonna have to build me a Slacktave. I have a 4024 in my modular, but none in my parts drawer, so I guess I'll use a 4013 - I have a few of those spare.


EDIT: Just found a spare 4024 in my static-proof CMOS vault/Faraday cage. Cool! Is there a perf layout anywhere?

[Boogdish]

I already have a modded slacktave version 1, but this looks much cooler.  Maybe it's time to upgrade.

[aziltz]

EDIT: Just found a spare 4024 in my static-proof CMOS vault/Faraday cage. Cool! Is there a perf layout anywhere?

speaking of...  an engineer once asked me, (a physicist) if i had a spare faraday cage...  

[frequencycentral]

OK, so the MkII octup uses a 4070 quad 2 input exclusive OR gate. I don't have any, but I do have some 4077 quad 2 input exclusive NOR gate, the truth table for a NOR gate is exactly opposite that of a OR gate. Am I right in assuming it should work in this application, the octave will just be inverted?


EDIT: I also wonder what difference it would make if the fundamental extractor is fed into the 4070, which is then fed into the 4024. So using the first three outputs of the 4024, you would (pesumably) get the original note but squared (which would sound quite synthy compared to the output of the fundamental extractor?), then 1 and two octaves down. Would this be the case? If so I think I might prefer a square wave of the original note to a "nasty comparator fuzz". Maybe? Or would it be essentially the same thing?

[slacker]

Q- Is this just a schematics "typo" or is there something I'm missing here?? I am using two TL072

Yeah that's a typo, the opamps should be the same as in the original schematic, sorry about that. I'll correct the schematic tomorrow if I get time.

Rick, I think the 4077 should work, the fact that the octave up is inverted won't matter.
I don't think using the 4070 to drive the 4024 will make any difference. The third opamp section is a comparator so that already gives you a square wave, I don't think the output of the 4070 will sound any different.

[frequencycentral]

Thanks Ian, I'll put a perf layout together to fit with my current 'wrong way round' enclosure series, with all the pots onboard the perf. I've had those CMOS chips knocking around for ages, I hope they work!

[solderman]

Q- Is this just a schematics "typo" or is there something I'm missing here?? I am using two TL072

Yeah that's a typo, the opamps should be the same as in the original schematic, sorry about that. I'll correct the schematic tomorrow if I get time.

Rick, I think the 4077 should work, the fact that the octave up is inverted won't matter.
I don't think using the 4070 to drive the 4024 will make any difference. The third opamp section is a comparator so that already gives you a square wave, I don't think the output of the 4070 will sound any different.

No problem. It actually got me thinking and analysing why and how this thing works insted of just "building" it so it's actually for the better.

[slacker]

Corrected schematic is here http://www.aronnelson.com/gallery/main.php/v/slackers-stuff/album170/slacktavemkII.jpg.html

[Fuzz Aldryn]

BTW this thing has is a "killer sound" so I am really keen to get it to work. By the samples I have heard. Especially that one that starts with a Wha and adds a Phase90. That smells Kraftwerk. Bet you cloud play "Autobahn" with this one   

http://forum.musikding.de/cpg/thumbnails.php?album=300

Thank's Slacker for designing it and Helge for those recordings I just love them.

Hi,

thank you for your kind words - I feel honored.
Yeah I realy dig that kind of tb 303 sounds you can get with it - espacialy in the -1 mode. I did a minor mod to it though: I changed the octave down mix pot to a 100k lin. To me it sounds  this way even more like a synthy.
As I'm realy proud of it here's a pic of it again - in the case slacker hasn't seen it yet. slacker, this is my way to say thank you.


At the moment I'm thinking about something like that - could take the slacktave to another dimension or at least to the mkIII. But I haven't got the guts to do it on my own - my best diy mate is on holydays. anyway, that's what I'm thinking about it:


Regards
Helge

[frequencycentral]

This is how I'm planning to build my MKII, with a volume pot for each octave. I put it past Ian, he made some improvements (thanks Ian!), though he's way ahead of me and was already planning something similar plus some for the MKIII. I'm just working on the perf layout.

[slacker]

That was quick Rick, nice work.

That looks great Helge, what are the little switches for?

[Fuzz Aldryn]

That was quick Rick, nice work.

That looks great Helge, what are the little switches for?

Hi,

nice work of yours, too. The three switches are for the octave modes. From above to down: -1/-2, off/-3, off/+1. Yes, you even can get a third octave down if you connet pin 9 of the 4024 - though it sounds reeeeaaaly weird. But I decides to make everything possible that was possible!:D But I got still problems with the octave up. It doesn't break through like in your samples with the octave down blended full out and sometimes it squeals like a cricket:D
@Ian: Great idea to have some seperats pots for the octaves. No it needs only some envolope conrolled vcf and vca.

Regards
Helge

[frequencycentral]

But I got still problems with the octave up. It doesn't break through like in your samples with the octave down blended full out and sometimes it squeals like a cricket:D

Check out the 100uf cap at the vref on Slacker's new schematic, and on my modification. That might help!

[Fuzz Aldryn]

But I got still problems with the octave up. It doesn't break through like in your samples with the octave down blended full out and sometimes it squeals like a cricket:D

Check out the 100uf cap at the vref on Slacker's new schematic, and on my modification. That might help!

Hi Ian,

thanks -  I was already thinking about that. Might be the reason as I did not included it. I'll gonna test it tomorrow as I realy fall asleep atm.

Regards
Helge

[slacker]

No it needs only some envolope conrolled vcf and vca.

That should be possible. Depends on how complicated you want it to be, I was thinking of adding a simple VCF to the next version something like one of Tim Escobedo's quick and dirty ones or the one from the Music From Outer Space WSG.
It would be easy to add a couple of simple Attack/Decay generators and a VCA as well.

If you want something more like real synth filters and VCAs then it might be best to build those as separate units or have a look at the MFOS Sub commander guitar synth.

[Fuzz Aldryn]

Hi Ian,

I attached a newer version of my oct up daughter board. Is it correct?

Thank you!

Regards
Helge

[solderman]

This is how I'm planning to build my MKII, with a volume pot for each octave. I put it past Ian, he made some improvements (thanks Ian!), though he's way ahead of me and was already planning something similar plus some for the MKIII. I'm just working on the perf layout.

Hi. This looks very interesting. I will try this since I still have the original on my bread board and it will be quit east to re arrange.

Q- I see that you have altered the 220n cap to the 4024 to 100n. If I have calculated correct it, together with the 100K pot all the way (100K) it will cut at 16Hz but at 10K it will cut at 156 witch I find a bit high??
With 220n the same is 7.2 and 72 Hz??

Just wondering if this is intended ??





   

[frequencycentral]

Hi. This looks very interesting. I will try this since I still have the original on my bread board and it will be quit east to re arrange.

Q- I see that you have altered the 220n cap to the 4024 to 100n. If I have calculated correct it, together with the 100K pot all the way (100K) it will cut at 16Hz but at 10K it will cut at 156 witch I find a bit high??
With 220n the same is 7.2 and 72 Hz??

Just wondering if this is intended ??

No, that's a mistake it should be 220n as you say. I breadboarded this the other day, though I have to work out some issues, as I'm losing signal somewhere in the fundamental extractor. I'm also planning to add some wave shaping and I've kludged up this little circuit:



I haven't tried it yet, so it will need tweaking. The idea is that the first two opamps form an integrator to turn the square into a rough triangle/trapezoid, the "Shape" control defining the angle of the triangle/trapezoid. The third opamp/PNP tranny gets a sawtooth from the triangle/square, that bit I stole from nicolas3141 at electro-music.com: http://electro-music.com/forum/viewtopic.php?t=27934&sid=c1ec97a6487c38767b97ee03e38143d1

[solderman]

Hi
I have been testing a fiev thing on the bread board and this is my latest mod. I have used 2 TL072 and used the 1:st and the 3:d op-amp stage on the first TL72 and the 2:nd an 4:th on the 2:d TL072. This is because of PCB layout routing reasons I wanted to test this setup. I don't know if this is the reason but I have found that the effect of the pots was minimal and narrow so I supst them for 4 SPST:s. one of them is the 3:d oct down (thank's Helge) Instead I invoked a "boostable" (trim pot) dry signal amd made the dry and effected signal separately mixable in to OUT. I also invoked a switch to kill the "clean" square signal so I can mix the  dry with the "only octave" Also supsted the 15K on op amp 1 to 33K to boost the signal that I found "choppy" I don't know why this is though but the signal chops and makes a terrible noise otherwise.